MYTUTOR SUBJECT ANSWERS

How can aldehydes and ketones be distinguished?

Firstly note that in general aldehydes are more reactive than ketones. This is a result of two effects:

1. Ketones are more sterically hindered.

2. Alkyl groups are electron donating and so reduce the partial positive charge on the carbonyl carbon.

As a consequence of this difference in reactivity aldehydes are oxidised more easily than ketones and so, by selecting a sufficiently weak oxidising agent, we can distinguish the two functional groups by oxidising one but not the other.

Fehling's Test

The test begins as two separate solutions - Fehling's A and Fehling's B. The first is a light blue CuSO4 solution while the second is a solution of a chelate and sodium hydroxide.

Equal volumes of the two solutions are mixed and the sample is added. The resulting solution is heated.

“I’m AD, a medical student at Bristol and I offer Biology, Chemistry and personal statement tutoring!”

This tutor has experience on our Schools Programme, which means they have worked with education professionals to provide one-to-one tuition in
schools across the country. They have been trusted by teachers to deliver high quality, in-depth lessons which complement what students learn in
class.

“I am a first year medical student at the University of Birmingham. My teaching sessions will be tailored around each student, going at their pace.”

This tutor has experience on our Schools Programme, which means they have worked with education professionals to provide one-to-one tuition in
schools across the country. They have been trusted by teachers to deliver high quality, in-depth lessons which complement what students learn in
class.

“I am a passionate medical student who would love to teach the sciences and maths to any willing student! I would also love to help prospective medical students achieve their dreams!”

This tutor has experience on our Schools Programme, which means they have worked with education professionals to provide one-to-one tuition in
schools across the country. They have been trusted by teachers to deliver high quality, in-depth lessons which complement what students learn in
class.

About the author

“About Me: As a second year chemist at Oxford University I naturally have a love for anything and everything science. Science can be challenging at times however, with the right approach, it can be anengaging and exciting subject. I ho...”

This tutor has experience on our Schools Programme, which means they have worked with education professionals to provide one-to-one tuition in
schools across the country. They have been trusted by teachers to deliver high quality, in-depth lessons which complement what students learn in
class.